Radiation protection during PET/CT

Imaging with equipment that combines positron emission tomography and computed tomography (PET/CT) provides the special benefits of both in one procedure. It is a highly sensitive imaging technique used in oncology, cardiology, neurology and in infectious and inflammatory diseases. 

The information from the PET scan and from the CT scan is different but complementary. The PET scan shows areas with increased metabolic activity, while the CT scan shows detailed anatomical locations. A combination of these two images enables a doctor to tell whether a region with high metabolic activity is significant, and if so, to state definitively where that location is. 

Often the PET/CT is repeated to monitor the effect of treatment of a particular disease. Most commonly PET utilizes 18F-FDG as a radiotracer, the short half-life of which (110 min) reduces radiation exposure compared with other commonly used radionuclides such as 99mTechnetium (6 hours) and 201Thallium (72 hours).

The radiation exposure from 18F results in internal exposure to the patient and low level external exposure to other people in their vicinity. The radiation (X-rays) from the CT scanner only radiates the patient and only during the CT scan. Whenever a repeat PET/CT scan is necessary, it should be performed with low dose CT.